The present invention relates to a method for display context synchronization for a display system of an aircraft, as well as to a display system with synchronized display context.
The present invention applies to a display system exhibiting a distributed architecture and comprising a plurality of units, each of said units comprising:                a viewing screen able to display one of a plurality of different formats; and        a control panel comprising actuation means allowing an operator to control the display on the viewing screen of one of said formats so as to present it in accordance with a particular display context which represents a display configuration. Said display context defines a set of particular options (scale, mode of display, type of symbology, etc.) which can be selected by the pilot via means of actuation of the control panel for the associated format.        
When said display system is intended for a transport airplane, in particular a military transport airplane, a significant number of formats (or display formats) are accessible for selection on the flight deck of this airplane. A format illustrates the set of display data which form part of one and the same flight function such as short-term piloting, navigation or management of tactical systems for example. On a tactical transport airplane, a display system can comprise at least some of the following formats:                a PFD (“Primary Flight Display”) format which displays primary flight parameters;        an NTD format which illustrates a tactical navigation format;        an EWD (“Engine Warning Display”) format which corresponds to a format for monitoring engine parameters and for optionally generating alerts;        an SD (“System Display”) format which corresponds to a format illustrating the statuses of systems of the airplane;        a video format which represents a format displaying images taken by cameras of the airplane;        an FM (“Flight Management”) format;        a TM format for managing tactical systems of the airplane;        an AD format for managing in-flight drop phases; and        a FUEL format for managing in-flight refueling phases.        
In order to ensure high operational effectiveness, each pilot is generally free to display the formats that he wishes, at any moment, on the viewing screens allocated thereto, using the associated control panels for this purpose. He can also freely configure their display context, in particular according to the flight phases.
Thus, during a flight containing several different tactical missions (drop, refueling, low-altitude flight, overflying of a hostile zone, etc.), the pilot of a military transport airplane will freely choose the format to be displayed on each viewing screen allocated thereto, so as to adapt it to his mission. For this purpose, the pilot may have in particular:                to swap the formats on two different screens; and        to redisplay a previously displayed format (for example following a fault with another screen or in the event of managing a new flight situation).        
Consequently, such a display system of aforesaid type is particularly well suited to a military transport airplane since, by virtue of the aforesaid freedom of format selection, it allows the pilot to adapt the information presented by this display system to his mission. Moreover, certain formats permit a very large number of different configurations, thereby making it possible to respond effectively to the requirements of different missions.
However, such a display system exhibits a significant drawback. It gives rise to a significant workload for the pilot or pilots of the airplane, which workload is not always compatible with the demands (flight management, monitoring of the environment of the airplane, etc.) of a tactical mission such as aforesaid.
Furthermore, as the display system considered in the present invention exhibits a distributed architecture, that is to say an architecture where each unit is independent of the other units and therefore does not comprise any data concentrator or master computer (or unit) which coordinates the action of the other units, it is not possible to provide a central facility for managing the display contexts so as to reduce this workload.